1. Field of the Invention
The present disclosure relates generally to the recovery of subterranean deposits and more specifically to methods and systems for sampling non-contaminated or representative hydrocarbons within a well.
2. Description of Related Art
Wells are drilled at various depths to access and produce oil, gas, minerals, and other naturally-occurring deposits from subterranean geological formations. The drilling of a well is typically accomplished with a drill bit that is rotated within the well to advance the well by removing topsoil, sand, clay, limestone, calcites, dolomites, or other materials. The drill bit is typically attached to a drill string that may be rotated to drive the drill bit and within which drilling fluid, referred to as “drilling mud” or “mud”, may be delivered downhole. The drilling mud is used to cool and lubricate the drill bit and downhole equipment and is also used to transport any rock fragments or other cuttings to the surface of the well.
As wells are established it is often useful to obtain information about the well and the geological formations through which the well passes. Information gathering is typically performed using tools that are delivered downhole by wireline or alternatively tools that are coupled to or integrated into the drill string. Wireline-delivered tools are suspended from a wireline that is electrically connected to control and logging equipment at the surface of the well. The tools may be deployed by first removing the drill string and then lowering the wireline and tools to an area of interest within the formation. This type of testing and measurement is often referred to as “wireline formation testing (WFT).” The tools associated with WFT may be used to measure pressure and temperature of formation and wellbore fluids.
Instead of wireline deployment, measurement tools are sometime coupled to or integrated with the drill string. In these situations, the added expense and time of removing the drill string prior to measurement of important formation properties is avoided. This process of “measurement while drilling (MWD)” uses measurement tools to determine formation and wellbore temperatures and pressures, as well as the trajectory of the drill bit. The process of “logging while drilling (LWD)” uses tools to determine additional formation properties such as permeability, porosity, resistivity, and other properties. The information obtained by MWD and LWD allow operators to make real-time decisions and changes to ongoing drilling operations.
Collecting a representative sample of formation or reservoir fluids (typically hydrocarbons) is often desired to further evaluate drilling operations and production potential. However, formation fluids near the wellbore are often contaminated by drilling mud and other non-formation-originating fluids injected into the well during drilling operations. These contaminating fluids seep into the formation adjacent the wellbore and provide an impediment to collecting an uncontaminated sample of formation fluid.